The present invention is directed to a drilling and/or chiseling tool including a housing with an axially extending guide tube projecting out of the housing in a working direction of the tool. A striking mechanism is mounted in the guide tube and includes a first piston reciprocating in the guide tube with a free second piston located ahead of the first piston toward a leading end of the guide tube with the two pistons arranged to form an air cushion between them. A driving anvil is located within the guide tube ahead of the second piston and arranged to be driven by the second piston as the first piston is reciprocated and the second piston is correspondingly reciprocated via the air cushion. The guide tube has at least one air passage extending radially therethrough located in the range between the first and second pistons. A control body displaceable in the working direction is arranged to selectively close the air passage. The control body includes a first stop for contacting a first stop shoulder on the driving anvil and the first stop is displaceable opposite to the working direction against the biasing action of a spring.
German patent 26 41 070 discloses a drilling and/or chiseling tool with a guide tube, a piston in a striking mechanism and a second piston arranged axially movable in the guide tube. Between the two pistons, the guide tube has a radially extending air passage which can be closed by a control body and the control body can be displaced axially relative to the guide tube.
When the air passage is open, the interior of the guide tube is ventilated whereby pressure cannot be developed by the piston of the striking mechanism which is necessary for the axial displacement of the other piston in the working direction. When the air passage is closed by the control body, a pressure can be developed within the guide tube between the two pistons. A stop on the control body, formed as a base, interacts with a first stop shoulder of a driving anvil arranged co-axially in the guide tube so that it can be driven axially.
Before a receiving material is worked by the tool and before the tool is started, a drilling or chiseling bit inserted in the tool chuck is pressed against the receiving material with great force. At the same time, the drilling or chiseling tool, as well as the driving anvil, is guided and the control body interacting with the driving anvil is shifted relative to the tool housing opposite to the working direction so that the control body, after closing the air passages, is located against a stop edge of the tool housing facing in the working direction.
When the tool is lifted from the receiving material after a working operation has been completed, the air passage should be released or opened as quickly as possible so that the striking mechanism piston no longer develops a pressure and cannot reciprocate the other piston, the driving anvil, and the drilling or chiseling bit in the working direction. A rapid release of the air passage is obtained due to the fact that the control body is displaced as rapidly as possible in the working direction into its starting position.
Since the total contacting force is transferred by the control body to the housing, the control body must be constructed very solidly and have a very high strength and, accordingly, a high weight. Rapid shifting of such a solidly formed control body in the working direction is effected by a strong spring, also of a heavy construction, supported at the housing of the tool counter to the working direction and interacting with the control body. The high weight of the spring and control body have a negative effect on the total weight of the tool. Due to its high total weight, the tool is difficult to anvil and the operator tires rapidly.